Incidence of clinical mastitis in dairy herds in England

The annual incidence of clinical mastitis was measured in 144 Holstein/Friesian dairy herds in England (average size 132 cows) during 1994, 1995 and 1996 by means of carefully defined mastitis indices. The mean annual incidence-of the disease over the three-year period,vas 43.4 quarter-cases per 100 cows, and the disease affected 25.9 per cent of the cows in the herds, with 1.6 quarter-cases per affected cow. In terms of cow-cases, the mean incidence was 39.9 cases per 100 cows in the herd and hence the ratio of quarter-cases to cow-cases was on average 1:1. The proportion of repeat quarter-cases was on average 19.4 per cent, and the recurrence rate was 18.3 per cent. The new infection rate was 28.3 per cent.